diff --git a/hyracks-fullstack/algebricks/algebricks-core/src/main/java/org/apache/hyracks/algebricks/core/algebra/prettyprint/LogicalOperatorPrettyPrintVisitorJson.java b/hyracks-fullstack/algebricks/algebricks-core/src/main/java/org/apache/hyracks/algebricks/core/algebra/prettyprint/LogicalOperatorPrettyPrintVisitorJson.java
index e56a8bd..f4e8003 100644
--- a/hyracks-fullstack/algebricks/algebricks-core/src/main/java/org/apache/hyracks/algebricks/core/algebra/prettyprint/LogicalOperatorPrettyPrintVisitorJson.java
+++ b/hyracks-fullstack/algebricks/algebricks-core/src/main/java/org/apache/hyracks/algebricks/core/algebra/prettyprint/LogicalOperatorPrettyPrintVisitorJson.java
@@ -171,6 +171,10 @@
     @Override
     public Void visitAggregateOperator(AggregateOperator op, Integer indent) throws AlgebricksException {
         addIndent(indent).append("\"operator\": \"aggregate\"");
+        if (!op.getExpressions().isEmpty()) {
+            addIndent(0).append(",\n");
+            pprintExprList(op.getExpressions(), indent);
+        }
         variablePrintHelper(op.getVariables(), indent);
         return null;
     }